Shift work and menstruation: A meta-analysis study

BACKGROUND: Shift work is a potential risk factor for women's reproductive health. Evidence suggests that shift work is associated with menstrual disorders, reproductive disturbances, and adverse pregnancy outcomes. However, previous studies did not systematically examine the results of menstrual irregularities, dysmenorrhea, and early menopause at the same time. OBJECTIVE: To determine the relationship between shift work and women's menstrual characteristics (e.g., irregular menstruation, dysmenorrhea, and early menopause). METHODS: Four databases (PubMed, Embase, Cochrane, and Web of Science) were searched up to December 2022. The study characteristics and risk assessment values of the literature were extracted from 21 studies that met the criteria. Odds ratios (ORs), relative risks (RRs), hazard ratios (HRs), and 95% confidence intervals (CIs) were calculated to assess the relationship between shift work exposure and menstruation. The included studies were evaluated for heterogeneity, publication bias, sensitivity analysis, and subgroup analysis. RESULTS: A total of 21 studies with 195,538 female participants, including 16 cross-sectional studies and 5 cohort studies, were included in this meta-analysis. According to the quality evaluation, the included research had high methodological quality. The overall ORs of shift work for the likelihood of irregular menstruation and dysmenorrhea were 1.30 (95% CI, 1.23–1.36) (I(2) = 41.9%, P < 0.05) and 1.35 (95% CI, 1.04–1.75) (I(2) = 73.0%, P < 0.05), respectively. There was a significant positive association between shift work and the risk of early menopause (HR = 1.09, 95% CI, 1.04–1.14), without significant heterogeneity (I(2) = 0.0%, P > 0.05). CONCLUSIONS: This meta-analysis indicated that shift workers have significantly higher odds of menstrual disorders, dysmenorrhea, and early menopause. This study focuses on female reproductive health and has broad implications for adjusting optimal working hours and shift schedules for female workers.